【作者】 谭江；

【导师】 黄百渠；

【作者基本信息】 东北师范大学 ， 细胞生物学， 2008， 博士

【摘要】 间充质干细胞(MSCs)是一种非胚胎来源的成体干细胞,并且具有自我更新能力和分化的多潜能性。目前研究表明,染色质的表观修饰对于干细胞的状态至关重要。本研究采用启动子芯片(ChIP-on-chip)和基因表达谱芯片(expression microarray)技术,首先对人骨髓来源的间充质干细胞的组蛋白H3-Lys9表观修饰和基因表达状态在基因组水平上进行了分析鉴定,结果表明人骨髓间充质干细胞基因启动子区H3-Lys9的乙酰化和二甲基化状态与基因的表达水平密切相关。另外,我们发现这些受启动子区H3-Lys9表观修饰状态调控的基因与一系列维持细胞分化多潜能性的重要的生物学功能通路相关,如细胞信号相关通路,细胞周期相关通路以及细胞因子相关通路等。而后又在人骨髓来源的间充质干细胞成骨分化过程中在基因组水平上对组蛋白H3-Lys9表观修饰和基因表达变化情况进行分析。我们发现在人骨髓来源的间充质干细胞成骨分化过程中组蛋白H3-Lys9整体乙酰化水平下降,而二甲基化水平显著上升。而且我们还鉴定出在人骨髓来源的间充质干细胞成骨分化过程中mRNA表达水平受表观修饰调控的基因,而这部分基因与一系列细胞分化过程中所必需的生物学事件相关,如细胞周期停滞、细胞内骨架重塑等。此外我们还发现维生素D受体可能在间充质干细胞成骨分化过程中参与到H3-Lys9去酰化和甲基化,进而使所调控的基因发生转录抑制。由此我们认为基因启动子区H3-Lys9乙酰化和二甲基化所控制的基因开关,以及由此引起的某些细胞通路的激活与关闭,不仅在维持人骨髓间充质干细胞的自我更新和增殖状态过程中发挥着重要的作用;而且对于其成骨分化过程的顺利推进同样至关重要更多还原

【Abstract】 Mesenchymal stem cells (MSCs) of non-embryonic origins possess the self-renewal and multi-lineage differentiation potentials. It has been established that epigenetic mechanisms such as histone modifications could be critical for determining the fate of stem cells. In this study, full human genome promoter microarrays and expression microarrays were used to examine the roles of histone modifications (H3-Lys9 acetylation and dimethylation) in regulation of gene expression in human bone marrow MSCs and upon MSC osteogenic differentiation. We showed that modifications of histone H3-Lys9 at gene promoters correlated well with mRNA expression in human bone marrow MSCs. Functional analysis revealed that many key cellular pathways in human bone marrow MSC self-renewal, such as the canonical signaling pathways, cell cycle pathways and cytokine related pathways may be regulated by H3-Lys9 modifications. Our results also revealed that the enrichment of H3-Lys9 acetylation was decreased globally at the gene promoters, whereas the number of promoters enriched with H3-Lys9 dimethylation was increased evidently upon osteogenic induction. By combined analysis of data from both ChIP-on-chip and expression microarrays, a number of differentially expressed genes monitored by changes of H3-Lys9 acetylation and/or dimethylation were identified, implicating their roles in several biological events, such as cell cycle withdraw and cytoskeleton reconstruction that were essential to differentiation process. In addition, our results also showed that vitamin D receptor played a trans-repression role via alternations of H3K9Ac and H3K9Me2, upon MSC osteogenic differentiation. Our data suggest that gene activation and silencing affected by H3-Lys9 acetylation and dimethylation, respectively, may be essential to the maintenance of human bone marrow MSC self-renewal, multi-potency and differentiation process. This study provides information about genes that are important for MSC self-renewing and osteogenic differentiation, as well as the epigenetic mechanisms that regulate their expression.更多还原